Starting from the observation that colour charge is only well defined
on gauge invariant states, we construct perturbatively gauge invariant
, dynamical dressings for individual quarks. Explicit calculations sho
w that an infra-red finite mass-shell renormalisation of the gauge inv
ariant, dressed propagator is possible and, further, that operator pro
duct effects, which generate a running mass, may be included in a gaug
e invariant way in the propagator. We explain how these fields may be
combined to form hadrons and show how the interquark potential can now
be directly calculated. The onset of confinement is identified with a
n obstruction to building a non-perturbative dressing. We propose seve
ral methods to extract the hadronic scale from the interquark potentia
l. Various extensions are discussed.